U.S. patent application number 10/592677 was filed with the patent office on 2007-08-30 for hydraulic transmission actuator.
This patent application is currently assigned to Dr. Ing h.c.F. Porsche Aktiengesellschaft. Invention is credited to Serge Nassif.
Application Number | 20070199394 10/592677 |
Document ID | / |
Family ID | 34961873 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070199394 |
Kind Code |
A1 |
Nassif; Serge |
August 30, 2007 |
Hydraulic Transmission Actuator
Abstract
A hydraulic transmission actuator has a piston/cylinder unit in
which an actuating piston longitudinally displaceably arranged in
the cylinder housing divides the cylinder chamber into at least two
pressure chambers which can be acted upon by hydraulic oil by way
of control conduits. A piston rod is connected with the actuating
piston, and a sealing element is arranged on the actuating piston.
The sealing element seals off the two pressure chambers from one
another. The diameter of the cylinder housing is locally reduced
for increasing the radial contact pressure force of the sealing
element with respect to the interior cylinder wall.
Inventors: |
Nassif; Serge; (Mundolsheim,
FR) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Dr. Ing h.c.F. Porsche
Aktiengesellschaft
Porscheplatz 1
Stuttgart
DE
70435
|
Family ID: |
34961873 |
Appl. No.: |
10/592677 |
Filed: |
March 17, 2005 |
PCT Filed: |
March 17, 2005 |
PCT NO: |
PCT/EP05/02830 |
371 Date: |
September 13, 2006 |
Current U.S.
Class: |
74/335 |
Current CPC
Class: |
Y10T 74/19251 20150115;
F15B 15/1447 20130101 |
Class at
Publication: |
074/335 |
International
Class: |
F16H 61/00 20060101
F16H061/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 2004 |
DE |
10 2004 022 722.5 |
Claims
1-5. (canceled)
6: Hydraulic transmission actuator comprising a piston/cylinder
unit having an actuating piston system longitudinally displaceably
arranged in a cylinder housing so as to divide the cylinder chamber
into at least two pressure chambers which are actable upon by
hydraulic oil by control conduits, at least one piston rod
connected with the actuating piston system, and a sealing element
arranged on the actuating piston system, to seal off the pressure
chambers from one another, wherein the diameter of the cylinder
housing is locally reduced for selectively increasing the radial
contact pressure force of the sealing element with respect to an
interior wall of the cylinder housing.
7: Hydraulic transmission actuator according to claim 6, wherein a
diameter of the cylinder housing in a left and right operating
position spaced from a center position of the actuating piston
system is reduced with respect to a diameter of the cylinder
housing in the center position of the actuating piston system.
8: Hydraulic transmission actuator according to claim 6, wherein a
diameter of the cylinder housing, starting out from left and right
operating positions, widens in a direction of the respective end
position of the actuating piston and, in two end positions, has a
diameter substantially the same as in a center position of the
actuating piston system.
9: Hydraulic transmission actuator according to claim 8, wherein a
diameter of the cylinder housing in a left and right operating
position spaced from a center position of the actuating piston
system is reduced with respect to a diameter of the cylinder
housing in the center position of the actuating piston system.
10: A hydraulic transmission actuator according to claim 6, wherein
the actuating piston system and the cylinder housing have a stepped
construction.
11: In an automatic standard transmission, an actuating element for
a gear change comprising a piston/cylinder unit having an actuating
piston system longitudinally displaceably arranged in a cylinder
housing so as to divide the cylinder chamber into at least two
pressure chambers which are actable upon by hydraulic oil by
control conduits, at least one piston rod connected with the
actuating piston system, and a sealing element arranged on the
actuating piston system, to seal off the pressure chambers from one
another, wherein the diameter of the cylinder housing is locally
reduced for selectively increasing the radial contact pressure
force of the sealing element with respect to an interior wall of
the cylinder housing.
12: In the automatic standard transmission according to claim 11,
wherein a diameter of the cylinder housing in a left and right
operating position spaced from a center position of the actuating
piston system is reduced with respect to a diameter of the cylinder
housing in the center position of the actuating piston system.
13: Hydraulic transmission actuator according to claim 11, wherein
a diameter of the cylinder housing, starting out from left and
right operating positions, widens in a direction of the respective
end position of the actuating piston and, in two end positions, has
a diameter substantially the same as in a center position of the
actuating piston system.
14: In the automatic standard transmission according to claim 11,
wherein the actuating piston system and the cylinder housing have a
stepped construction.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] The present invention relates to a hydraulic transmission
actuator having piston/cylinder unit in which an actuating piston
longitudinally displaceably arranged in the cylinder housing
divides the cylinder chamber into at least two pressure chambers
which can be acted upon by hydraulic oil by control conduits, and
having a piston rod connected with the actuating piston as well as
having a sealing element arranged on the actuating piston, by means
of which sealing element the two pressure chambers are sealed off
from one another.
[0002] Hydraulic transmission actuators are used, for example, in
the case of automated standard transmissions for synchronizing the
transmission gears (see, for example, Johannes Lohmann,
"Zahnradgetriebe", 2nd Edition, Page 156, and on).
[0003] In hydraulic transmission actuators of the above-mentioned
type, the actuating piston bounded by two pressure chambers is
displaced toward the left or right as a result of correspondingly
being acted upon by pressure, with a sealing element being provided
for sealing off the two pressure chambers on the actuating piston.
When using hydraulic transmission actuators, high actuating forces
have to be applied, for example, when synchronizing the
transmission gears. The actuating forces require a reliable and
durable sealing-off and separating of the two pressure
chambers.
[0004] It is, therefore, an object of the present invention to
improve the sealing-off of the two pressure chambers in the area of
the actuating piston.
[0005] This object is achieved by providing that the diameter of
the cylinder housing is locally reduced for increasing the radial
contact pressure force of the sealing element with respect to the
interior cylinder wall.
[0006] For increasing the radial contact pressure force of the
sealing element with respect to the interior cylinder wall, the
diameter of the hydraulic cylinder is advantageously locally
reduced in an area in which high actuating forces act upon the
actuating piston.
[0007] In a left and right operating position deviating from the
center position of the actuating piston in the hydraulic cylinder,
the diameter of the hydraulic cylinder is reduced in comparison to
the diameter of the hydraulic cylinder in the center position of
the actuating piston. As a result, in both operating positions of
the actuating piston, a higher contact pressure force of the
sealing element is achieved with respect to the interior cylinder
wall.
[0008] The diameter of the hydraulic cylinder widens after passing
through both operating positions, so that the contact pressure
force of the sealing element with respect to the interior cylinder
wall is adapted to the reduced actuating forces.
[0009] As a result of the fact that the actuating piston and,
therefore also, the cylinder housing have a stepped construction,
in a first adjusting path with a small piston diameter, a high
adjusting speed can be achieved with low friction, while, in the
two operating positions, the hydraulic force acts upon the large
piston diameter, so that a higher radial contact pressure force of
the sealing element against the interior wall of the cylinder
housing can be generated.
[0010] The hydraulic transmission actuator can be used particularly
as an actuating element for synchronizing transmission gears in the
case of automated standard transmissions.
[0011] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic view of a hydraulic transmission
actuator according to the present invention in a first operating
position;
[0013] FIG. 2 is a schematic view of the transmission actuator
shown in FIG. 1 but in a second operating position;
[0014] FIG. 3 is a schematic view of the transmission actuator
shown in FIG. 1 but in a third operating position;
[0015] FIG. 4 is a schematic view of the transmission actuator
shown in FIG. 1 but in a fourth operating position; and
[0016] FIG. 5 is a schematic view of the transmission actuator
shown in FIG. 1 but in a fifth operating position.
DETAILED DESCRIPTION OF THE DRAWINGS
[0017] The transmission actuator 2, which is preferably used as an
actuating element for the synchronization or for a gear change in
the case of an automated standard transmission, has a cylinder
housing 4 in whose cylinder chamber 6 a double-acting actuating
piston 8 is received in a longitudinally displaceable manner. The
actuating piston 8 is constructed as a step piston and has a
central piston 8a which is guided in the cylinder chamber 6 and is
adjoined by a left and a right actuating piston element 8b, 8c. On
its circumferential surface, the central piston 8a has a sealing
ring 10 which mutually seals off the two partial cylinder chambers
6a, 6b separated by the central piston 8a. The two actuating piston
elements 8b, 8c, whose diameters are reduced in comparison to the
central piston 8a, are longitudinally displaceably guided in a left
and a right cylinder housing part 4b, 4c, respectively. One piston
rod 12, 14 respectively is fastened to the left and the right
actuating piston element 8b, 8c. Each piston rod 12, 14 is sealed
off at the end of the left and the right cylinder housing part 4b,
4c toward the outside by way of one sealing device 16, 18
respectively.
[0018] One hydraulic conduit 24, 26 respectively is connected to
the partial chambers 20, 22 formed in the left and in the
respective cylinder housing part 4b, 4c, such that each hydraulic
conduit 24, 26 allows hydraulic oil to act upon the two partial
chambers 20, 22.
[0019] As illustrated in FIG. 1, the diameter of the central
cylinder housing part 4a does not have a uniform construction along
its length l but, in the center position of the central piston 8a
as well as at its left and right end respectively, which
corresponds to the end positions of the actuating piston 8, has a
maximal diameter D1, while the diameter is continuously reduced
starting from the left and right end and from the center position
of the central piston 8a. At the two positions W1, W2 illustrated
by a dash line in FIG. 1, the diameter of the central housing part
4a with its diameter D2 reaching a minimum on each side thereof.
The radial contact pressure force of the sealing ring 10 with
respect to the interior cylinder wall is the greatest when the
actuating piston reaches one of these two operating positions W1 or
W2 (see, for example, FIG. 3 with the arrows representing
force).
[0020] The hydraulic transmission actuator when used as an
actuating element for the gear change in an automated standard
transmission (which includes, for example, also the so-called
double-clutch transmission) operates as follows.
[0021] The center position of the central piston 8a corresponds to
the neutral position N, while the left end position of the
actuating piston 8, corresponds, for example, to an engaged gear 1,
and the right end position of the actuating piston 8 corresponds,
for example, to an engaged gear G3. As generally known, for
changing a gear, the establishment of a non-rotatable connection is
necessary between a sliding sleeve unit non-rotatably but
longitudinally displaceably arranged on the transmission shaft and
a loose gear assigned to the sliding sleeve unit. For equalizing
the different rotational speeds of the transmission shaft and the
loose gear, a synchronizing unit, made for example, by Borg-Warner,
is required which is arranged between the sliding sleeve unit and
the loose gear.
[0022] In the following description, the synchronization or the
gear change from position N to the odd gear G3 will be explained in
detail by reference to FIGS. 1 to 5. As a result of an admission of
pressure to the partial chamber 20 by way of the hydraulic conduit
24, a hydraulic force acts for a first adjusting path upon the face
of the left actuating piston element 8b and causes a corresponding
displacement of the actuating piston 8. When, as indicated in FIG.
2, the left actuating piston element 8b is guided out of the left
cylinder housing part 4b, the hydraulic force acts upon the left
face of the central piston 8a which has a larger diameter. While,
in the case of the first adjusting path, because of the smaller
piston surface, a high adjusting speed is achieved while friction
is low, the adjusting speed is reduced and reaches its minimum
when, as illustrated in FIG. 3, the operating position W2 is
reached by the central piston 8a. In this position, in which the
radial contact pressure force of the sealing ring 10 is the
greatest with respect to the interior cylinder wall, the
synchronization takes place for the gear G3. After a synchronism
has been reached between the sliding sleeve unit and the loose
gear, the shifting-through of the gear can take place. Thereby,
because of the reexpanding diameter of the central cylinder housing
part 4a, the adjusting speed of the actuating piston 8 is increased
again.
[0023] Of course, the use of the transmission actuator is not
limited to an actuating element for the gear change in an automated
standard transmission. The transmission actuator of the present
invention can be used wherever, as a function of the adjusting path
of the actuating piston, different demands are made on the
sealing-off of the two pressure chambers separated by the central
piston 8a.
* * * * *